Ultrafast magnetization dynamics in the half‐metallic Heusler alloy Co2Cr0.6Fe0.4Al

Ultrafast demagnetization upon excitation with intense laser pulses has been observed for a variety of ferromagnetic materials. In half-metals, long demagnetization times are expected due to the band gap for one spin direction. We have investigated the theoretically half-metallic Heusler alloy Co2Cr0.6Fe0.4Al (CCFA), using the time-resolved magnetooptical Kerr effect. A demagnetization time in the range of typical transition metal ferromagnets with lower spin polarization has been found, while magnetization recovery proceeds on a slower time scale. The results are discussed in the context of recent models and experimental results. We propose that for Heusler alloys the initial stage of recovery could be a better measure for the spin polarization than the demagnetization time. A simple estimate leads to a bulk spin polarization value of 0.86 for CCFA. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim